In the related art, an optical module including a photoelectric conversion element (light-emitting element, light-receiving element or both) is used in optical communications using an optical transmission member such as an optical fiber and a light waveguide. In an optical module, an optical receptacle that is disposed between a photoelectric conversion element and an optical transmission member and is configured to optically couple the photoelectric conversion element and an end surface the optical transmission member is used. Optical modules are classified into a transmitting optical module having a transmitting capability and a receiving optical module having a receiving capability, and a transmitting and receiving optical module having both a transmitting capability and a receiving capability.
For example, as an optical module for transmission, an optical module that is intended to adjust the optical output or stabilize the output performance of a light emitting element against temperature variation, and includes a detection element for checking (monitoring) the intensity and the quantity of the emission light emitted from the light emitting element is known (see, for example, PTL 1).
FIG. 1 schematically illustrates a configuration of optical module 10 disclosed in PTL 1. In FIG. 1, the hatching on the cross-section of optical receptacle 30 is omitted to illustrate light paths in optical receptacle 30.
As illustrated in FIG. 1, optical module 10 disclosed in PTL 1 includes photoelectric conversion device 20 and optical receptacle 30. Optical receptacle 30 includes first optical surface 31 that allows incidence of emission light L emitted from light-emitting element 21, reflection surface 32 that reflects emission light L having entered optical receptacle 30 from first optical surface 31 toward optical transmission member 40 side, light separation part 33 that separates emission light L reflected by reflection surface 32 into monitor light Lm travelling toward detection element 22 side and signal light Ls travelling toward optical transmission member 40 side, transmission surface 34 that allows signal light Ls emitted out of optical receptacle 30 by light separation part 33 to reenter optical receptacle 30, second optical surface 35 that emits signal light Ls having entered optical receptacle 30 from transmission surface 34 such that the light is condensed at the end surface of optical transmission member 40, and third optical surface 36 that emits monitor light Lm toward detection element 22.
Reflection surface 32 is a part of the inner surface of first recess 37 formed in the top surface of optical receptacle 30. In addition, light separation part 33 is a part of the inner surface of second recess 38 formed in the top surface of optical receptacle 30.